19366-15-5Relevant academic research and scientific papers
Insertion of Diazo Esters into C-F Bonds toward Diastereoselective One-Carbon Elongation of Benzylic Fluorides: Unprecedented BF3Catalysis with C-F Bond Cleavage and Re-formation
Wang, Fei,Nishimoto, Yoshihiro,Yasuda, Makoto
supporting information, p. 20616 - 20621 (2021/11/23)
Selective transformation of C-F bonds remains a significant goal in organic chemistry, but C-F insertion of a one-carbon-atom unit has never been established. Herein we report the BF3-catalyzed formal insertion of diazo esters as one-carbon-atom sources into C-F bonds to accomplish one-carbon elongation of benzylic fluorides. A DFT calculation study revealed that the BF3 catalyst could contribute to both C-F bond cleavage and re-formation. This elongation provided α-fluoro-α,β-diaryl esters with a high level of diastereoselectivity. Various benzylic fluorides and diazo esters were applicable. The synthetic utility of this method was demonstrated by the synthesis of a fluoro analogue of a compound that is used as a transient receptor and potential canonical channel inhibitor.
A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
, p. 6684 - 6690 (2021/05/31)
Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
Superelectrophilic Fe(III)-Ion Pairs as Stronger Lewis Acid Catalysts for (E)-Selective Intermolecular Carbonyl-Olefin Metathesis
Albright, Haley,Schindler, Corinna S.,Vonesh, Hannah L.
supporting information, p. 3155 - 3160 (2020/04/21)
An intermolecular carbonyl-olefin metathesis reaction is described that relies on superelectrophilic Fe(III)-based ion pairs as stronger Lewis acid catalysts. This new catalytic system enables selective access to (E)-olefins as carbonyl-olefin metathesis products. Mechanistic investigations suggest the regioselective formation and stereospecific fragmentation of intermediate oxetanes to be the origin of this selectivity. The optimized conditions are general for a variety of aryl aldehydes and trisubstituted olefins and are demonstrated for 28 examples in up to 64% overall yield.
A new method for reductive coupling of carbonyl compounds to olefins
Kumar Dutta,Konwar
, p. 6227 - 6229 (2007/10/03)
Aromatic and aliphatic aldehydes and ketones react with AlCl3-Zn in acetonitrile to yield olefins in good yield. (C) 2000 Published by Elsevier Science Ltd.
Development of a polymer bound Wittig reaction and use in multi-step organic synthesis for the overall conversion of alcohols to β-hydroxyamines
Bolli, Martin H.,Ley, Steven V.
, p. 2243 - 2246 (2007/10/03)
An efficient combinatorial access to β-hydroxyamines suitable for automation is achieved by the mild oxidation of alcohols to aldehydes by polymer supported perruthenate (PSP), the subsequent clean olefination of the obtained aldehydes by polymer supported Wittig reagents followed by the epoxidation of the olefins by dimethyldioxirane (DMDO), and the final aminolysis of the epoxides with various amines is described.
Studies on the synthesis of chiral 2-(p.chlorophenyl)-3-methylbutanoic acid, a key-precursor of Fenvalerate, by hydrocarbonylation reactions
Botteghi, Carlo,Bona, Denis Dalla,Paganelli, Stefano,Marchetti, Mauro,Sechi, Barbara
, p. 101 - 107 (2007/10/03)
The preparation of racemic 2-(p.chlorophenyl)-3-methylbutanoic acid (2), a building block for (S,S)-Fenvalerate (an important broad spectrum insecticide), was effected by rhodium catalyzed hydroformylation of 2-methyl-1 -(p.chlorophenyl) propene (4) in the presence of excess of triphenylphosphine to inhibit substrate isomerization followed by mild oxidation of the resulting aldehyde 6; an overall yield of 88% was reached. Olefin 4 exhibits a very low tendency to undergo both hydrocarboethoxylation and hydrocarboxylation in the presence of palladium complexes as catalysts. Enantioselective hydrocarbonylation reactions carried out on olefin 4 afford unsatisfactory chemical and optical yields of the optically active ester 5 or acid 2. Springer-Verlag 1996.
Distinction between polar and electron-transfer routes. A mechanistic study on the wittig reactions of nonstabilized ylides
Yamataka, Hiroshi,Nagareda, Katsushi,Takatsuka, Tsutomu,Ando, Katsuhiro,Hanafusa, Terukiyo,Nagase, Shigeru
, p. 8570 - 8576 (2007/10/02)
The Wittig reaction of nonstabilized ylides with benzaldehyde and benzophenone was investigated in detail by means of carbonyl-14C kinetic isotope effects, substituent effects, and isotope-scrambling and probe experiments. The reaction with benzophenone gave the carbon isotope effects and the Hammett ρ values of considerable magnitude both in Li salt-free and salt-present conditions. In contrast, they are quite small for the reaction with benzaldehyde. Enone-isomerization and dehalogenation probe experiments indicated that the nonstabilized ylide has enough ability to transfer an electron to benzaldehyde and benzophenone. These results were interpreted in a self-consistent manner by the mechanism that the Wittig reaction of nonstabilized ylides proceeds via initial electron transfer from the ylide to the carbonyl compounds. The electron-transfer step is rate-determining for benzaldehyde, while radical coupling following the electron-transfer step is rate determining for benzophenone. From the probe experiments together with the isotope effects and the substituent effects reported previously, the reaction of semistabilized ylides was concluded to proceed through a polar nucleophilic addition mechanism.
OLEFIN SYNTHESIS VIA THE LITHIUM DERIVATIVE OF THE N,N,N',N'-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS. 3. SYNTHESYS OF SOME β-DISUBSTITUTED STYRENES
Momchilova, Snejana,Petrova, Jordanka,Kirilov, Marko
, p. 319 - 328 (2007/10/02)
The reaction of Li-derivatives of N,N,N',N'-tetramethyldiamides of arylmethanephosphonic acids (1-Li) with alkanones, cycloalkanones, alkylaryl- and diarylketones 2a-h is studied.It is found that in THF at -70 deg C adducts 3-Li and 4-Li are formed, the corresponding hydroxyl compounds 3 and 4 being isolated in 36-81percent yields, while by elevated temperatures the reaction is completely shifted to the starting 1-Li and 2.By thermolysis of 3 and 4 in neutral medium olefins 5 and 6 are obtained even from readily enolysable ketones.The stereochemistry of the addition reaction with nonsymmetrical ketones as well as the influence of the substituents at the carbonyl groups on the conformation and adsorption properties of the adducts are discussed.
Thermal fragmentation of 3-alkyl-2-phenyloxetanes, 3,3-dimethyl-2-aryloxetanes, and related compounds. A case study of 2-aryl-substituted oxetanes
Imai, Toshiro,Nishida, Shinya
, p. 2503 - 2509 (2007/10/02)
Thermolyses of epimeric 3-alkyl-2-phenyloxetanes (1c, 1t, 2c, 2t, 3c, and 3t), 3,3-dimethyl-2-aryloxetanes (4, 5, 6, 7, and 8), 3,3,4,4-tetramethyl-2,2-diphenyloxetane (9), and 3,3-dimethyl-2,2-diphenyloxetane (10) were studied in degassed N,N,N',N'-tetramethylethylenediamine at 270-350 deg C.Although the fragmentation of 9 and 10 can be understandable on the basis of a diradical mechanism, there were several observations, in the reaction of certain other oxetanes, which could hardly be explained simply in terms of such a mechanism.Namely, (1) less strained 1t reacted faster than more strained 1c; (2) a major mode of the fragmentation for 1c, 2c, and 3c was "B" (forming an alkene and benzaldehyde), whereas that for 1t, 2t, and 3t was "A" (forming an alkenylbenzene and formaldehyde); (3) the apparent energy of activation for the "B" process seemed to be larger than that for the "A"; (4) a dramatic change of the major fragmentation mode from "B" to "A" was brought about by a substituent on the phenyl group, as was observed in 4-8.These results may be explained reasonably by assuming that the fragmentation proceeds, at least, in dual reaction courses.In competition with an anticipated diradical pathway, there will be another process, which is energetically little more favorable than the diradical fragmentation, rather specific to the "A" mode fragmentation, and important particularly in the reaction of the trans isomers.Probable candidates for the second process are discussed.
